If the 3GS does have issues with the update, they could always un-underclock it. It's what, 833 MHz underclocked to 600MHz? They could lift that to 700 MHz or so, while including smarter methods of CPU/GPU usage, thus decreasing the amount of heat dispersed and rate of battery drain. The 3G wasn't able to keep up I think because they had not done that. The 3G had the same processor as the 2nd gen iPod touch, and it was underclocked to 412MHz, whereas the 2nd gen iPod touch was clocked at I think it was 537MHz? Some non-even number that made me go all obsessive-compulsive over it. That was the biggest killer on the iPhone 3G IMHO.